Dirty Rotten Flieger Posted April 10, 2015 Share Posted April 10, 2015 I just bought the K4 on sale and I am pleasantly surprised. I didn't enjoy flying the dora when I couldn't balance the ground trim tabs for balanced cruise and I was expecting the same problems but the K4 is perfectly trimmed to climb at around the range of 400km/h, 1.4ata, 2500rpm . which feels great in a plane that out climbs it's opponents. Really a joy to fly... If I can get off the ground . Love the sound of the beefy engine. I noticed the leading edge slats deploy at much higher speed and lower angle of attack than I expected. I imagine this is increasing lift and drag at speeds when it is isn't needed. I don't know exact speed but they pop out closer to 380km/h than 250km/h which was not what I would expect. Maybe my expectations were wrong, but I thought the slats were just for close to stall speed. Not nearly 400km/h Anyway great plane, and beautiful model. Glad I bought it . Link to comment Share on other sites More sharing options...
gavagai Posted April 10, 2015 Share Posted April 10, 2015 Stalling depends of angle of attack, not airspeed. That is why you see the slats deploy at 400km/h.:thumbup: P-51D | Fw 190D-9 | Bf 109K-4 | Spitfire Mk IX | P-47D | WW2 assets pack | F-86 | Mig-15 | Mig-21 | Mirage 2000C | A-10C II | F-5E | F-16 | F/A-18 | Ka-50 | Combined Arms | FC3 | Nevada | Normandy | Straight of Hormuz | Syria Link to comment Share on other sites More sharing options...
IIIJG52_Otto_ Posted April 11, 2015 Share Posted April 11, 2015 Stalling depends of angle of attack, not airspeed. That is why you see the slats deploy at 400km/h.:thumbup: are you sure? what AoA do you have in a flat spin?:music_whistling: http://www.jagdgeschwader52.net Link to comment Share on other sites More sharing options...
alfredo_laredo Posted April 11, 2015 Share Posted April 11, 2015 are you sure? what AoA do you have in a flat spin?:music_whistling: A lot... Aoa its the angle between the relative wind and the chord of the wing A.K.A. Timon -117th- in game Link to comment Share on other sites More sharing options...
IIIJG52_Otto_ Posted April 12, 2015 Share Posted April 12, 2015 (edited) ;)A lot... Aoa its the angle between the relative wind and the chord of the wing Tell me .. what´s "a lot" AoA for you in a flat spin? :D fall like a brick is to fly at high AoA? Edited May 8, 2015 by III/JG52_Otto_+ http://www.jagdgeschwader52.net Link to comment Share on other sites More sharing options...
ZaltysZ Posted April 12, 2015 Share Posted April 12, 2015 Tell me .. what´s "a lot" AoA for you in a flat spin? :D Something like 65-90 degrees. Wir sehen uns in Walhalla. Link to comment Share on other sites More sharing options...
Exorcet Posted April 12, 2015 Share Posted April 12, 2015 I always read the term "stall speed" in the aircraft performances chart, never "Stall AoA". Stall speed is the speed where the the AoA required for flight is the stall AoA. AoA is what matters for stall. Thinking it's speed is a common mistake. we only need a enougt powerfull engine. ;) You can fly on brute force, but then you're not an airplane. Awaiting: DCS F-15C Win 10 i5-9600KF 4.6 GHz 64 GB RAM RTX2080Ti 11GB -- Win 7 64 i5-6600K 3.6 GHz 32 GB RAM GTX970 4GB -- A-10C, F-5E, Su-27, F-15C, F-14B, F-16C missions in User Files Link to comment Share on other sites More sharing options...
alfredo_laredo Posted April 12, 2015 Share Posted April 12, 2015 ;) I always read the term "stall speed" in the aircraft performances chart, never "Stall AoA". I think, If we have enough airspeed, we will have lift, the AoA is indiferent, we only need a enougt powerfull engine. ;) The airflow parallel and opposite to the direction of flight is the relative wind, within this airflow its the wing, generating lift. The imaginary line between the leading edge and the trailing edge of the wing its called "chord line" The angle between the relative wind and the chord line its the angle of attack. The maximun angle of attack at wich the wing its capable of generating sufficient lift to sustain flight is the critical angle of attack. When the angle of attack exceeds the critical angle of attack the aircraft stalls. So.... You never heard of stall AOA. well thats because its simplier to know and for the pilot read the stall speed. remember not all aircrafts have an AOA indicator. your statement of If we have enough airspeed, we will have lift, the AoA is indiferent, we only need a enougt powerfull engine its wrong. If you have enough speed, you will keep the AOA in its limits (because of lower AOA). AOA its never indiferent. and you dont need a powerfull enough engine, better speaking you need anough Airspeed (more relative wind) Now you may be confused with this. AOA its not the angle between the wing and the grond horizon. You can have a plane flying 90° up and still have a lower AOA. or in your case a level flying with high AOA (flat spin) por example. Salute! A.K.A. Timon -117th- in game Link to comment Share on other sites More sharing options...
Ala13_ManOWar Posted April 12, 2015 Share Posted April 12, 2015 (edited) You can fly on brute force, but then you're not an airplane.That's called ballistic, I think. But that's not flying, it's just a rocket. You can stall any airplane at any speed, just pull enough AoA and you'll get it. Slats are deployed on stall, if they were deployed on speed you would stall all the time without slats working and they would deploy only at Vs, or minimum flight speed. But minimum speed stall is only one of the ways you can stall an airplane. An airplane stalls because AoA (even mínimum speed stall is because AoA) so you can stall it at any speed-many situations. S! Edited April 12, 2015 by Ala13_ManOWar "I went into the British Army believing that if you want peace you must prepare for war. I believe now that if you prepare for war, you get war." -- Major-General Frederick B. Maurice Link to comment Share on other sites More sharing options...
ZaltysZ Posted April 12, 2015 Share Posted April 12, 2015 (edited) I always read the term "stall speed" in the aircraft performances chart, never "Stall AoA". I think, If we have enough airspeed, we will have lift, the AoA is indiferent, we only need a enougt powerfull engine. ;) There is usually no "Stall AoA", but sometimes "Critical AoA" is given, or more often, even whole chart of AoA vs CL (lift coefficient) is presented. Lift depends on both speed and CL, and CL depends on AoA. Stall speed is just lowest speed at which aircraft can stay at flight while being at critical AoA. Increase AoA past it, and you won't stay at level flight even if your speed indicator shows stall speed. You can compensate low CL with high speed, and low speed with high CL (high AoA), but within limits (CL past Critical AoA begins to decrease sharply). You can't have one of them at zero, or near zero without making other impossibly high. Edited April 12, 2015 by ZaltysZ Wir sehen uns in Walhalla. Link to comment Share on other sites More sharing options...
sobek Posted April 12, 2015 Share Posted April 12, 2015 You can stall any airplane at any speed You can't stall an airplane (much) above its corner airspeed. It will simply disintegrate. Good, fast, cheap. Choose any two. Come let's eat grandpa! Use punctuation, save lives! Link to comment Share on other sites More sharing options...
Ala13_ManOWar Posted April 12, 2015 Share Posted April 12, 2015 You can't stall an airplane (much) above its corner airspeed. It will simply disintegrate.Well, disintegration is sorta stall :lol:. Yeah, it would be quite difficult to get over G's and controls stiffening to pull enough, but technically not impossible. Just an example. S! "I went into the British Army believing that if you want peace you must prepare for war. I believe now that if you prepare for war, you get war." -- Major-General Frederick B. Maurice Link to comment Share on other sites More sharing options...
Echo38 Posted April 13, 2015 Share Posted April 13, 2015 You can't stall an airplane (much) above its corner airspeed. It will simply disintegrate. Like that one SR-71 that stalled while supersonic and broke up. But it did stall, briefly. Link to comment Share on other sites More sharing options...
Ala13_ManOWar Posted April 13, 2015 Share Posted April 13, 2015 Like that one SR-71 that stalled while supersonic and broke up. But it did stall, briefly.Or sad Air France Airbus accident couple of years ago. S! "I went into the British Army believing that if you want peace you must prepare for war. I believe now that if you prepare for war, you get war." -- Major-General Frederick B. Maurice Link to comment Share on other sites More sharing options...
Hummingbird Posted April 13, 2015 Share Posted April 13, 2015 The slats deploy at any speed if the AoA exceeds 11.5 deg, as they work by principle of airpressure, raising the overall lift of the wing to the level of the wing root section. Link to comment Share on other sites More sharing options...
I.ZG15_FALKE Posted April 14, 2015 Share Posted April 14, 2015 the manual explains it all ... pg 33: The wing of the 109 is made with no washout, i.e. with the same angle from wing root to wingtip. Most Allied fighters of the time were designed with the angle of incidence greater at the wing root and decreasing across the span, becoming lowest at the wing tip. This gives the 109's wing increased lift compared to similar Allied fighters, while the tip stalling problem normally solved by washout on other designs is solved on the 109 with the use of automatic leading-edge slats that normally extend before the wingtip can stall. The overall result is an excellent high-lift wing that is also difficult to stall. Link to comment Share on other sites More sharing options...
Ala13_ManOWar Posted April 14, 2015 Share Posted April 14, 2015 pg 33: The wing of the 109 is made with no washout, i.e. with the same angle from wing root to wingtip. Most Allied fighters of the time were designed with the angle of incidence greater at the wing root and decreasing across the span, becoming lowest at the wing tip. This gives the 109's wing increased lift compared to similar Allied fighters, while the tip stalling problem normally solved by washout on other designs is solved on the 109 with the use of automatic leading-edge slats that normally extend before the wingtip can stall. The overall result is an excellent high-lift wing that is also difficult to stall.Good to know!! I guessed it, but didn't know for sure. Anyway, now I'm not sure why a constant AoA wing even though using slats would be better than twisted ones in stall characteristics. Slats increases drag while twist doesn't for instance. S! "I went into the British Army believing that if you want peace you must prepare for war. I believe now that if you prepare for war, you get war." -- Major-General Frederick B. Maurice Link to comment Share on other sites More sharing options...
Kurfürst Posted April 14, 2015 Share Posted April 14, 2015 Slats increases drag while twist doesn't for instance. S! Twist however decreases AoA and hence lift, thus to get the same lift you need higher AoA which results in more drag. Gaps of the slats might give some small rise in parasite drag but they are closed most of the time, so their effect on parasite drag is probably miniscule. And when they are open you are actually better off with them, since they energize the airflow which amounts to much less drag than a turbulant airflow in the same condition without them! http://www.kurfurst.org - The Messerschmitt Bf 109 Performance Resource Site Vezérünk a bátorság, Kísérőnk a szerencse! -Motto of the RHAF 101st 'Puma' Home Air Defense Fighter Regiment The Answer to the Ultimate Question of the K-4, the Universe, and Everything: Powerloading 550 HP / ton, 1593 having been made up to 31th March 1945, 314 K-4s were being operated in frontline service on 31 January 1945. Link to comment Share on other sites More sharing options...
IIIJG52_Otto_ Posted April 14, 2015 Share Posted April 14, 2015 the manual explains it all ... pg 33: The wing of the 109 is made with no washout, i.e. with the same angle from wing root to wingtip. Most Allied fighters of the time were designed with the angle of incidence greater at the wing root and decreasing across the span, becoming lowest at the wing tip. This gives the 109's wing increased lift compared to similar Allied fighters, while the tip stalling problem normally solved by washout on other designs is solved on the 109 with the use of automatic leading-edge slats that normally extend before the wingtip can stall. The overall result is an excellent high-lift wing that is also difficult to stall. Twist however decreases AoA and hence lift, thus to get the same lift you need higher AoA which results in more drag. Gaps of the slats might give some small rise in parasite drag but they are closed most of the time, so their effect on parasite drag is probably miniscule. And when they are open you are actually better off with them, since they energize the airflow which amounts to much less drag than a turbulant airflow in the same condition without them! Very well said friends! .. I think that explains perfectly the main funtion of the automatics slats in the Bf-109 wings. :thumbup: http://www.jagdgeschwader52.net Link to comment Share on other sites More sharing options...
Hummingbird Posted April 14, 2015 Share Posted April 14, 2015 the manual explains it all ... pg 33: The wing of the 109 is made with no washout, i.e. with the same angle from wing root to wingtip. Most Allied fighters of the time were designed with the angle of incidence greater at the wing root and decreasing across the span, becoming lowest at the wing tip. This gives the 109's wing increased lift compared to similar Allied fighters, while the tip stalling problem normally solved by washout on other designs is solved on the 109 with the use of automatic leading-edge slats that normally extend before the wingtip can stall. The overall result is an excellent high-lift wing that is also difficult to stall. Yep, but without explaining why all of that is the case in minute detail there will always be some people who purposely misinterpret the above :doh: There's a bloody reason that every modern pilot (which incl. some of the most experienced in the world) who've flown both the Bf-109 and Spitfire say that the difference in turning capability is very small between these two fighters (with a slight edge to the Spitfire mind you), and that pilot proficiency would be the deciding factor. Hence it's little wonder that RAF & LW veterans often can't agree what aircraft turned tighter, as they've both seen "evidence" to support their opinion :) Will be a glorious day that a modern test pilot sets out to record the exact characteristics of these two fine aircraft (and more) with a blackbox to record all the forces in flight to once and for all shut up all those who keep on clinging to 70 year old reports that have already been proven grossly inaccurate a million times but somehow still attract followers. Better still if the aircraft are exact reproductions with new repro engines so as not to be afraid of straining one of those old original engines, which is all that would be limiting such a test atm really as well as eliminating that as a possible excuse. Link to comment Share on other sites More sharing options...
gavagai Posted April 15, 2015 Share Posted April 15, 2015 There's a bloody reason that every modern pilot (which incl. some of the most experienced in the world) who've flown both the Bf-109 and Spitfire say that the difference in turning capability is very small between these two fighters (with a slight edge to the Spitfire mind you). The turn rates are close enough for at least one to say that the Bf 109 turns better!:crazy: P-51D | Fw 190D-9 | Bf 109K-4 | Spitfire Mk IX | P-47D | WW2 assets pack | F-86 | Mig-15 | Mig-21 | Mirage 2000C | A-10C II | F-5E | F-16 | F/A-18 | Ka-50 | Combined Arms | FC3 | Nevada | Normandy | Straight of Hormuz | Syria Link to comment Share on other sites More sharing options...
Hummingbird Posted April 15, 2015 Share Posted April 15, 2015 (edited) The turn rates are close enough for at least one to say that the Bf 109 turns better!:crazy: Indeed. Also certain versions of the 109 will probably outturn certain versions of the Spitfire, which is what Skip Holm for example has suggested. And his words carry some weight seeing as he is one of the most experienced pilots out there, period, and probably the foremost authority on these old birds, having flown the majority of the them and not at all being afraid of testing them to their flight envelope limits in the process. (He enjoys mock dogfights in these old aircraft) Take a look at his resumé: http://www.skipholm.com/biography.htm Total Flight Time: Approximately 14000 hours in fighter types A-4, A-6, A-7, A-37, BD-5J, BD-10, F-4, RF-4, F-5, F-11, F-15, F-16, F-86, F-100, F-101, F-104, F-105, F-106, F-111, F-117, T-1, T-2, T-33, T-37, T-38, OV-1, O-2, OV-10, U-2, Casa, Draken J35, Fouga, Gnat T-1, L-29, L-39, Mig-15, Mig-17, Mig-21, Mig-23, Sepa jet, Soko, SU-27, Vampire, P-38, P-40, P-47, P-51, F-8, ME-109, Yak-3, Yak-8, Yak-11, Yak-50, Yak-55, Spitfire, Skyraider, Mosquito, Sea Fury, Corsair, T-6, T-28, T-41 (plus others) If we can't trust him, then who can we trust? Edited April 15, 2015 by Hummingbird Link to comment Share on other sites More sharing options...
[DBS]TH0R Posted April 15, 2015 Share Posted April 15, 2015 Will be a glorious day that a modern test pilot sets out to record the exact characteristics of these two fine aircraft (and more) with a blackbox to record all the forces in flight to once and for all shut up all those who keep on clinging to 70 year old reports that have already been proven grossly inaccurate a million times but somehow still attract followers. And which documents might that be? You yourself favor older documents instead of (more) modern revised ones. ;) P8Z68 | 2500k @ 4.5 | GTX 1080Ti | 2x8 GB @ 1600 | TM Hog (extended 7cm) & MFG Crosswind (S/N 007) | TIR v5 WWII bomber formations | DCS P-51D: [TEST] TO distance / gross weight / temperature Link to comment Share on other sites More sharing options...
Hummingbird Posted April 15, 2015 Share Posted April 15, 2015 And which documents might that be? You yourself favor older documents instead of (more) modern revised ones. ;) Oh no, I most certainly do not, and the reason is that it's easy to find old documents in complete contradiction with each other. The documents I'm talking about are period test flight report documents that many take as the definitive truth, eventhough most can easily be contradicted by other flight tests from the same period, not to mention easily disproven with the actual knowledge & experience we have with physically operating these aircraft today. Link to comment Share on other sites More sharing options...
[DBS]TH0R Posted April 16, 2015 Share Posted April 16, 2015 (edited) Oh no, I most certainly do not, and the reason is that it's easy to find old documents in complete contradiction with each other. The documents I'm talking about are period test flight report documents that many take as the definitive truth, eventhough most can easily be contradicted by other flight tests from the same period, not to mention easily disproven with the actual knowledge & experience we have with physically operating these aircraft today. Funny you should say that since we have seen the opposite from you, twice already. Apparently the document from 1944 is more accurate than the revision from 1954 that replaces it (after 10 years of service life!). Had you looked more closely you would have seen that the initial 1944 version is by large a direct copy from 1943 manual for an earlier version of the same plane. And all subsequent variants from 1945 to 1947 have more and more pieces from the original 1943 document deleted (that contradict one another) - up to the complete revision in 1954. But the latter one doesn't cater to your theoretical arguments. :) Here is a friendly advice to you: stop quoting others and selectively picking data which suites your theoretical arguments that you read somewhere and apparently take for granted. Instead, if you feel that something is off, do the math yourself. That way people might actually start listening to you since you do have some interesting things to say. Also, passively insulting people that their comments are "false and completely illogical" doesn't help you in winning them over either. EDIT: Referencing. Edited April 16, 2015 by T}{OR Refreshing Hummingbird's memory from 2 days ago. P8Z68 | 2500k @ 4.5 | GTX 1080Ti | 2x8 GB @ 1600 | TM Hog (extended 7cm) & MFG Crosswind (S/N 007) | TIR v5 WWII bomber formations | DCS P-51D: [TEST] TO distance / gross weight / temperature Link to comment Share on other sites More sharing options...
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